Case subjects are drawn from adolescents aged 10 to 18 previously seen at Western Psychiatric Institute and Clinic for evaluation, and meet the DSM-IIIR criteria for diagnosis of ADHD based on a structured parent interview and standardized parent and teacher rating scales. Cases were also systematically observed and evaluated in the summer treatment program between 1987 and 1996 at WPIC. Controls are demographically matched non-ADHD adolescents, recruited from surrounding communities and pediatric practices.